Refactor auto_release_obs.py to use a service run

[dcermak]

We currently rely on https://github.com/SUSE/osc-tiny/blob/f47ee8994fd65ab547b593162d58abfc72472ffb/auto_release_obs.py to update osc-tiny. It would be much nicer if we added a _service file to the package (or similar):

<services>
  <service name="obs_scm" mode="manual">
    <param name="url">https://github.com/SUSE/osc-tiny.git</param>
    <param name="scm">git</param>
    <param name="revision">v0.12.0</param>
    <param name="versionformat">@PARENT_TAG@</param>
    <param name="changesgenerate">enable</param>
    <param name="versionrewrite-pattern">v(.*)</param>
  </service>
  <service mode="manual" name="set_version"/>
  <service name="tar" mode="buildtime"/>
  <service name="recompress" mode="buildtime">
    <param name="file">*.tar</param>
    <param name="compression">gz</param>
  </service>
</services>

and then all we need is osc branchco; cd $_; osc service mr; osc ci -m "version bump"; osc sr -m "version bump" which is much cleaner and conforms more to OBS best practices.